As dyes usable for a use of photo-decoloring, a combination of a leuco dye or an azomethine dye with a acid generating agent is described in Japanese Patent Publication Open to Public Inspection (hereinafter referred to as JP-A) No. 5-10042, and an organic boric acid salt of a sensitizing dye is described in JP-A No.9-279081. Further, a guanidine salt dye of a pyrazolotriazole mother nucleus is disclosed in JP-A No. 5-96868.